This invention relates to a photographic recording apparatus for carrying out photo-recording on a photo-recording medium. For example, the present invention may be suitably applied to a color printer or the like which is adapted to form an image on a recording medium such as an instant or convenience film for photo-coloring or the like.
A color printer for irradiating light to a photosensitive material such as an instant color film or the like to write an image on the photosensitive material generally utilizes a refractive index distribution type lens array in order to simplify an optical system and reduce a manufacturing cost of the printer. The refractive index distribution type lens array is formed into a substantially cylindrical shape and has a refractive index distribution wherein a refractive index is decreased in a manner like a parabolic curve from a central axis thereof to an outer periphery thereof. Light incident on the refractive index distribution type lens travels in the lens while meandering at a predetermined cycle. The refractive index distribution type lens array is an optical element formed by precisely integratedly arraying a number of refractive index distribution type lenses while keeping central axes thereof parallel to each other and then securely arranging the thus-arrayed lenses between a plurality of flame plates. The optical system of the conventional color printer is so constructed that the refractive index distribution type lens array is arranged in proximity to a luminous surface of a luminous element in order to render a central axis of the refractive index distribution type lens array parallel to a light emission direction of the luminous element. The luminous element emits dot-like light for forming an image. The thus-emitted light is incident directly on the refractive index distribution type lens array and then discharged from the lens array, resulting in directly forming an erected image of an equi-magnification on an instant or convenience color film.
Unfortunately, such optical arrangement of the luminous element and refractive index distribution type lens array as described above causes a distance between the luminous surface of the luminous element and the image formed on the instant color film or an object-image surface distance (or conjugate length) to be substantially increased to a level as large as about 40 mm, resulting in failing in thinning of the color printer or formation of the color printer into a reduced thickness. A refractive index distribution type lens constructed so as to be decreased in object-image surface distance is commercially available. However, the commercially available lens is substantially increased in optical dispersion in the lens, to thereby readily cause occurrence of chromatic aberration which renders use of the lens as the optical element for the color printer fully impossible.